1. Field of Invention
This invention relates to image printing systems, and more particularly to eliminating blooming in ink jet printing.
2. Description of Related Art
The following patents are hereby incorporated by reference in their entirety: U.S. Pat. No. 6,513,909 to Elrod for its teaching of a method of forming and moving ink drops across a gap between a print head and a print medium in a marking device that includes generating an electric field, forming the ink drops adjacent to the print head and controlling the electric field; and U.S. Pat. No. 6,079,814 to Lean for its teaching of improved ink droplet placement on a recording medium.
A conventional method of forming and moving ink drops across a gap between a print head and a print medium, or an intermediate print medium in a marking device, includes generating an electric field, forming the ink drops adjacent to the print head, and controlling the electric field. The electric field is generated to extend across the entire gap, and the ink drops are formed in an area adjacent to the print head. Accordingly, the electric field is controlled such that an electrical attraction force exerted on the formed ink drops by the electric field is the largest force acting on the ink drops. Further, a transport belt may be electrostatically charged with a charge of one type so that an electrostatic pressure is generated and concurrently induces an opposite charge on the ink droplets ejected by the print head, thereby accelerating the droplets toward the recording medium by Coulombic attraction.
This electrostatic field assist improves drop directionality by providing a forward acceleration on the ink drops, thus reducing transit time and minimizing the effect of transverse disturbances. Also, spot placement errors due to variations in ejection velocity between adjacent nozzles are reduced because of the acceleration of the ink drops. Generally, the acceleration of the ink drops from rest rather than drawing on the initial velocity of the drop ejection reduces the power requirement by 40–50%. Accordingly, the combined effect is that more spherical drops are formed, which results in more circular spots and sharper edges on a printed image.